BUI:IETIN-No. 115 Biology of the bloodworm, Glycera dibranchiata Ehlers, and its relation to the bloodworm fishery of the Maritime Provinces By W. L. KLAWE and L. M. DICKIE Fisheries Research Board oj Canada Biological Station, St. Andrews, N.B. PUBLISHED BY THE FISHERIES RESEARCH BOARD OF CANADA UNDER THE CONTRO L OF THE HONOURABLE THE MINISTER OF FISHERIES tITAWA, 1957 rce 50 cents � �'[------------------------------------------------------------------------� BULLETIN No .. 115 Biology of the bloodworm, Glycera dibranchiata Ehlers, and its relation to the hloodw'orm fishery of the Maritime Provinces By w. L. KLAWE and L. M. DICKIE Fisheries Research BQard Qf Canada Biological Station, St. Andrews, N.B. PUBLISHED BY THE FISHERIES RESEARCH BOAR D OF CANADA UNDER THE CONTROL OF THE HONOURABLE THE MINISTER OF FISHERIES OTTAWA, 1957 91704--1 W. E. RICKER N. M. CARTER Editors 11 Bulletins of the Fisheries Research Board of Canada are published from time to time to present popular and scientific information concerning fishes and some other aquatic animals; their environment and the biology of their stocks; means of capture; and the handling, processing and utilizing of fish and fishery products. In addition, the Board publishes the following: An A nnual Report of the work carried on under the direction of the Board. The Journal of the Fisheries Research Board of Canada, containing the results of scientific investigations. Atlantic Progress Reports, consisting of brief articles on investigations at the Atlantic stations of the Board. Pacific Progress Reports, consisting of brief articles on investigations at the Pacific stations of the Board. The price of this Bulletin is 50 cents (Canadian funds, postpaid). Orders should be addressed to the Queen's Printer, Ottawa, Canada. Remittance made payable to the Receiver General of Canada should accompany the order. All publications of the Fisheries Research Board of Canada still in print are available for purchase from the Queen's Printer. Bulletin No. 110 is an index and list of publications of the Board and is priced at 75 cents per copy postpaid. iii 91704--H CONTENTS PAGE ABSTRACT. .. Vll INTRODUCTION. .. .. .. .. .. .. .. .. .. .. .. 1 Identity of Commercial Bloodworms...... .. .. .. 2 Classification.. .. .. .. .. 2 Morphology.. .. .. .. .. .. .. .. .. .. .. .. .. 3 Distribution.. .. .. .. .. .. .. .. .. .. 4 METHODS OF INVESTIGATION Measurement....... .. .. .. .. .. .. .. .. ... 4 Sampling..................................................... 5 Marking..................................................... 8 ECOLOGICAL OBSERVATIONS Distribution in the Intertidal Zone... .. .. .. 8 Fluctuations in Abundance.. .. .. .. .. .. .. .. 9 Extent of Movement... .. .. .. .. .. .. .. .. .. ... 11 Food Habits... .. .. .. .. .. .. .. .. .. .. .. .. 13 Poisonous Bites...... .. .. .. .. .. .. .. .. 14 LIFE-HISTORY STUDIES Sexual Maturation. .. 15 Spawning Season....... .. 16 Spawning.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 17 "Ghost" Worms............................. ....... .... ... ... 17 Swarming... ..... .................................. .. ....... , 18 Embryology.................................................. 19 Late Larval and Post-Larval Development.... .. .. .. 22 Size- and Age-Composition of Intertidal Populations........ .. 22 Growth Rates.. ... .. .. .. .. .. .. 27 THE FISHERY AND ITS EFFECTS Production, Labour Force and Income.. .. .. .. .. .. .. 29 Commercial Catches and Spawning Stock... .. .. .. .. .. .. 30 Relationship between Catch and Abundance........ .. .. .. .. 31 Prospects.. .. .. .. .. .. .. .. .. .. .. .. 34 ACKNOWLEDGMENTS. .. .. .. .. .. .. .. .. .. .. 35 REFERENCES. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 36 V ABSTRACT Commercial bloodworms (Glycera dibranchiata Ehlers) are found along both Atlantic and Pacific coasts of North America, from near high-water mark on the beach to a depth of at least 100 fathoms. This study treats only the intertidal populations in southwestern Nova Scotia. The worms are most abundant in soft muds, rich in organic materials, and rare in clear sandy soils. However, abundance in a flatvaries, showing long-term trends related to changes in soil condition, or short-term fluctuations of unknown causes. Bloodworms are not confined to single burrows but movements are limited. They seldom crawl on the surface of the mud or travel long distances by swimming, as do sandworms (Neanthes). They feed on organic detritus in the soil which helps explain their distribution. The function of their jaws and associated poison glands is in doubt but there is no good evidence that bloodworms are carnivores. Eggs and sperms begin development in late summer and the worms are sexually mature by early April. The principal spawning occurred in mid-May in 1953 and 1954, although a few "spawners" were still found in early June. Bloodworms die after spawning, resulting in the appearance of "ghost worms" on the flats. These consist of the outer skin and atrophied digestive tract with everted proboscis. There is no evidence for swarming at spawning time. In aquaria, development from the artificially-fertilized egg to the trocho­ sphere larva followed the pattern characteristic for the group. The trochlear ring formed about thirty-two hours after first cleavage and the larvae alternated short periods of rest with vigorous swimming. They died after about two weeks without further development. Attempts to collect them from plankton and intertidal flats were unsuccessful. Most of the intertidal population spawns when three years old but a small fraction spawns when four or five years old. Maximum life span appears to be five years. Growth rate is most rapid in the second and third years and decreases sharply thereafter. Maximum size observed was about 34 centimetres (13.5 in.) relaxed length. There is little or no growth in summer. The catch consists largely of sexually immature three-year-olds. But most bloodworms spawn in the spring at the beginning of their third year and die afterwards. The fishery is, therefore, supported mainly by the smaller fraction of this one age-class which does not spawn in spring, and there is little risk of depleting the stock by fishing. For the same reason catch in one year has little influence on catch in subsequent years so that restrictions on fishing would be useless as conservation measures. However, if the fishery becomes intense, annual catches will fluctuate in response to fluctuations in natural abundance of the stocks. The Nova Scotia stocks are lightly exploited now so such fluctuations are unlikely to interfere seriously with the present annual production of 4,000,000 worms or with expansion to about double the present volume. vii INTRODUCTION The regular rise and fall of the tides, periodically exposing the intertidal zone, invites examination of this small, easily-accessible part of the sea-bottom, and from time immemorial man has entered it to wonder at its many mysteries. Sometimes he has found food or objects useful in other ways. Sometimes he has only satisfied his curiosity. Among the most common of the creatures he has found are marine worms. Some of these have been of no obvious use. Others were eaten, and even to-day the famed Samoan palolo worm is esteemed as food by the islanders. But for a number of the polychaetous annelids man must early have found a use which has since played an important part in his social and cultural development. That is, a fish-hook baited with a marine worm is spiritedly taken by many fish and provides a ready source of food and recreation. Fish-hooks of various shapes, made of various materials, have been uncovered among remains of the dwellings of pre-historic man and his use of baited hooks for catching fish was certainly widespread. Bait-worms must have been employed in fishing for thousands of years. In modern times two marine polychaetous worms have a good reputation among salt-water sport fishermen on both the Atlantic and Pacific coasts of North America. Of these the bloodworm, Glycera dibranchiata (Ehlers) is the more important but there is also a demand for the sandworm, Neanthes virens (Sars), better known to scientists under its formerly accepted name, Nereis virens. The demand for these worms has created a small but active bait-worm industry which for the last 20 years has centred in the State of Maine. The landed value there in recent years has averaged about $200,000 annually. After the second world war increased demands for baitworms stimulated interest in potentially productive areas on the Canadian Atlantic coast. As a result the Fisheries Research Board of Canada began explorations for them. This exploratory work, carried out from the Biological Station at St. Andrews, New Brunswick (MacPhail 1954), led to the discovery of several areas where bloodworms were abundant-chiefly in the Wedgeport and Yarmouth districts of Yarmouth County, Nova Scotia. This fostered development of a small bloodworm industry new to Canada. Annual landings of about 4 million worms in 1954 and 1955 were valued at about $40,000 to the diggers. Little was known about bloodworms when our industry began but informa­ tion seemed desirable as a basis for judging its prospects and possible need for regulation. Accordingly a two-year biological investigation was undertaken in 1953 as a follow-up of the exploration program. This paper discusses features of the bloodworm's ecology, life-history and population dynamics which were discovered in the course of that study. It concludes